Geomorphic evidence for mid–late Holocene higher sea level from southeastern Australia

Abstract

An elevated sheltered pocket beach sequence at Batemans Bay, NSW, Australia, composed of shelly fine- to medium-grained sand provides geomorphic evidence of higher than present sea level during the mid–late Holocene. The sequence is composed of a sand facies with variable amounts of shell and contains a number of well-defined dipping reflectors identified in ground penetrating radar (GPR) profiles indicative of a small prograded beach system. This beach succession is overlain by storm or tsunami deposits. The beach deposit accumulated between 2500 and 5000 cal BP under relatively high energy conditions within a more open immature estuary during a period of higher sea level. Both deposits have been preserved by a low energy mangrove facies that accumulated after the recent fall in sea level cut off ocean wave activity from the area approximately 2000–2500 cal BP. This beach sequence provides new evidence for a period of higher sea level 1–1.5 m higher than present that lasted until at least c. 2000–2500 cal BP and adds complementary geomorphic evidence for the mid to late Holocene sea-level highstand previously identified along other parts of the southeast Australian coast using other methods.